I did GLAZED tiles. Yeah, scary.
White. Made sure they were clean. Stamped in StazOn, colors, sunflowers. No coloring needed.
The first time, I did not heat set. Let them dry, sprayed witih Fixatif. Send them off to sister. A few months later, she wiped one clean! Nothing toxic, just a good wipe cos it had got dirty. No more sunflower.
So I made her a replacement (I had scanned it). This time I heated it before I sealed it.
I also redid the tile she sent back to me - cleaned it off and restamped. Then I heated it but apparently there was still sealer around the edges, because it sort of browned. Which is not a bad idea if you want a weathered look.
So now I heat set before I seal it.
I got some tumbled tiles, and plan to follow the same general plan.